Clinical experience of the last 45 years has indicated that patients with paraplegia can learn to stand and ambulate with suitable orthotic assistance. Patients with paralysis of muscles innervated from the sacral to the middle thoracic segments of the spinal cord can be provided with means to stabilize the joints of the lower extremities which allows the patient to perform a variety of functional activities.
Thus, the use of orthotic devices to help support and control joints of the lower extremities following muscle paralysis is an important part of medical rehabilitation. However, the development of lower extremity orthotic devices has experienced few major breakthroughs in the past twenty five years. Conventional orthotic devices are awkward and cumbersome, particularly for the patient with generalized motor weaknesses. Moreover, these devices are exceedingly heavy, unattractive and must be permanently attached to the wearer's shoes. Furthermore, they tend to cause damage to clothing due to frictional wear, rough metal edges, and pinching joints.
Typically, one of four basic types of conventional lower extremity orthotic devices are prescribed for patients with various diagnostic problems resulting in unilateral paralysis, asymmetrical bilateral paralysis or total paralysis of the lower extremities: 1) a short leg brace known as an ankle-foot-orthosis (AFO), which has an adjustable, spring loaded ankle joint (Klenzak type); 2) a long-leg brace known as a knee-ankle-foot orthosis (KAFO), which has a free ankle joint and shoe modification; 3) a KAFO with an adjustable, spring-loaded ankle joint; and 4) a KAFO with controlled knee, free ankle motions and ischial weight-bearing support. Each of these conventional orthoses incorporates a permanent shoe-brace attachment.
For example, the Scott-Craig orthosis, a category (4) KAFO is most often prescribed for patients suffering injuries ranging from the sacral to the middle thoracic segments of the spinal cord (Lehmann et al. Phys. Arch. Med. Rehabil. 57: 438-442, 1976). These devices are long-leg braces with knee locks that are made of metal to withstand heavy-duty use.
Typically, a shoe base is constructed to provide a foundation upon which a pair of upright metal struts are attached by way of an ankle joint, and, traditionally, the shoe takes the form of a sole plate. However, these braces have significant drawbacks in that they are cumbersome, heavy, difficult to fit and adjust, difficult to apply and remove, and also very expensive. The cost of such braces, as well as the length of time required for their production, is significantly increased by the fact that they must be custom-made by an orthotist working with measurements taken from the individual patient. Even under ideal conditions, the period of time from when the braces are ordered to receipt by the patient typically requires several weeks. This produces the undesirable result of not having the braces available for use by the patient early in a rehabilitation program when, for trophic and psychological reasons, they are needed most to support standing. By the time they are finally fitted and in use by the patient, insufficient time may remain for adequate practice in using them. Consequently, these expensive appliances are often set aside within a few months after the patient leaves the hospital and thereafter, used very infrequently if at all (Priestly and Lehmkuhl, Phys. Ther. 62:660, 1982).
Moreover, since most conventional metal orthoses provide the wearer with, in a sense, an exoskeletal system to achieve the purposes of standing and limited ambulation, they do not utilize the patient's normal skeletal structure to carry a part of weight-bearing loads, even though it may be capable of carrying part or all of the body weight. The end result is braces that are too heavy and bulky to permit sufficient utilization of any residual motor functions that might be present.
Another drawback of conventional lower extremity orthoses is that the knee joints of such devices correspond poorly with the polycentric joint of the human knee, often resulting in an undesirable sliding motion when the patient walks, sits or stands. This undesirable motion can also lead to excessive wear and tear of clothing.
When new plastic materials became available, they were recognized as suitable replacements for the steel, aluminum and other metals formerly used to construct orthotic devices. The use of plastics in orthotics allowed orthotists to consider new design concepts, resulting in lighter and more cosmetically acceptable devices. For example, research at the Texas Institute for Rehabilitation and Research (TIRR) by the present inventor led to the development of a molded polypropylene ankle-foot orthotic device (AFO) which is worn inside the shoe. This AFO eliminated the mechanical ankle joint and brace shoe attachment of conventional braces and allowed the user the freedom to wear the device with his or her own shoe. (Engen, Orthotics and Prosthetics 26(4):1-15, 1972).
It was found, however, that AFO's constructed of unreinforced polypropylene were too flexible to provide sufficient dorsiflexion assistance. Therefore, corrugations were introduced into the molded AFO to strengthen those portions of the brace subjected to the greatest stress. The polypropylene AFO has an advantage in that it can be mass-manufactured and is modifiable after fabrication to ensure a proper fit.
In order to eliminate the drawbacks of conventional lower extremity orthotic devices, heretofore, there existed a need to incorporate the AFO into a structurally sound yet lightweight long-leg brace that is inexpensive to manufacturer and could be readily adapted to fit the user.
In accordance with the present invention, the lower extremity orthotic device has become even more lightweight, provides for an easier fit for the patient in a shorter amount of time, and enables the patient to manipulate the knee joints in a much easier fashion. It is also much less expensive, and is resistant to salt corrosion and sand so that a patient is less restricted in his or her outdoor activities.